bee in (someone's) bonnet

Translations
навязчивая идея
She has a bee in her bonnet about recycling.
У неё навязчивая идея по поводу переработки.
Definitions
To have an idea or thought that is constantly in someone's mind, often to the point of obsession or annoyance.
Words
bee

noun
пчела
in

preposition
в
someone

pronoun
кого-то
s

article or possessive pronoun
чей-то
bonnet

noun
шапочка